1. Field of the Invention
The present invention relates to a vibrator for a diaphragm pump and a magnet holder for it, and particularly to a vibrator for an electromagnetic diaphragm pump and a magnet holder for it. More specifically, the present invention relates to a vibrator and a magnet holder therefor in which it can be facilitated to coincide a central plane of the magnet holder with that of the magnet which is thinner than the magnet holder in the direction of their thickness when the magnet is attached to the magnet holder.
2. Description of the Prior Art
A conventional electromagnetic diaphragm pump is described by using the drawings. FIG. 8 is a cross-sectional view when the conventional electromagnetic diaphragm pump is seen from the front thereof, FIG. 9 is a plan view of the diaphragm pump of FIG. 8, and FIG. 10 is a side view along the X--X line of FIG. 9.
In these figures, a housing 1 is made by the press operation of a metal plate, and each of side plates 1A is punched with a circular hole 1B, the side plates being bent at both ends thereof so as to oppose each other.
A pair of diaphragm plates 2 made of an elastic material such as rubber are fitted into the circular holes 1B, respectively. The peripheral portion of each diaphragm 4 is pinched by and between corresponding the diaphragm plate 2 and a head cover 3, which are attached to the side plate IA of the housing 1 using screws 18.
A pair of plate-like magnets 8 are held in a plate-like magnet holder 6 which is a part of an electromagnetic diaphragm pump and preferably formed of a material such as aluminium. The pair of diaphragm 4 are attached to both ends of the magnet holder 6 by using pressing tools 5 and screws 7 The magnet holder 6 and magnets 8 constitute the vibrator of the electromagnetic diaphragm pump.
Inside each head cover 3, a diaphragm chamber 3A is formed. On each diaphragm chamber 3A, there are formed an intake port 14A and a discharge port 15A, which are provided with an intake valve 14 and a discharge valve 15, respectively.
Each field core 9 is an iron core of laminated silicon steel plates in the shape of "E", and, as shown in FIG. 9, the central leg thereof is fitted in a coil 11 wound around a bobbin 10.
The electromagnetic diaphragm pump is provided with two such field cores 9, which are fixed to the bottom of the housing 1 using bolts 12 and nuts 13 so as to sandwich the magnet holder 6. Since it is needed to support the field cores 9 apart from the bottom of the housing 1 by a predetermined distance, a sleeve 16 is passed through with the bolt 12 as shown in FIG. 10.
Such electromagnetic diaphragm pump is attached through, for instance, rubber vibration insulators 19, to a fluid tank 20 as seen in FIG. 8. A pressurized fluid such as air is discharged into the tank 20 as shown by an arrow C via a tube 17 connected to the head cover 3.
FIG. 11 is a schematic plan view for showing the operation principle of the electromagnetic diaphragm pump. In FIG. 11, the symbols same as those in FIG. 8 or FIG. 10 indicate the same or identical portions.
A pair of magnets 8 attached to the magnet holder 6 are arranged, as shown, so that the magnetic poles of the pair of magnets 8 are reverse to each other. Accordingly, if the coil is supplied with an a.c. current so that a magnetic flux passes from one field core 9 to the other field core 9 in the direction of a solid arrow P or a dotted arrow Q, the magnet holder 6 is reciprocated in the direction of an arrow R by the attractive and repulsive actions between the magnets 8 and a magnetic flux P or Q, whereby the diaphragm 4 is vibrated.
As a result, as shown in FIG. 9 by an arrow A, a fluid is sucked into the diaphragm chamber 3A through the side plate 1A of the housing 1, an opening 1D formed in the diaphragm plate 2 and head cover 3, the intake port 14A and intake valve 14, and the fluid passes through the discharge port 15A and discharge valve 15 and then the fluid is discharged from the tube 17 into the fluid tank 20 as shown by the arrow C in FIG. 8.
Such electromagnetic diaphragm pump is described in, for instance, the Japanese Patent Laid-open Publication No. Showa 61-252881 and the Utility Model Laid-open Publication Nos. Showa 63-100682 and 61-137892.
FIG. 12 is a plan view of the prior magnet holder 6, and FIG. 13 is a side view of the magnet holder 6. In these figures, the magnet holder 6 is formed of a non-magnetic material such as aluminium and has formed therein a pair of magnet insertion windows 6A in the main portion thereof and a pair of threaded holes 6B to be screwed with the screws 7 at the both ends (FIG. 8).
Each magnet insertion window 6A has a shape substantially same as the contour of the magnet 8, and the magnet 8 is inserted therein. After that, a bonding agent of the epoxy resin or the like is applied on the area of boundary between the magnet 8 and the window 6A, whereby the magnet 8 is fixed to the magnet holder.
The thickness of the magnet holder 6 is usually same as the thickness of the magnet 8. And, since the magnet 8 with comparatively small magnetic force can be used if the requested flow rate or output pressure of the electromagnetic diaphragm pump is small. The smaller the tickness of the magnet, the more inexpensive the cost of the electromagnetic diaphragm pump can be made, which is convenient. However, since the magnet holder 6 is required to have formed therein the threaded holes 6B for attaching the diaphragms 4, it is not allowed to be thinner than a certain thickness.
Therefore, sometimes the magnet holder 6 having a thickness greater than that of the magnet must be used for attaching the magnet. In this case, a predetermined jig is required for attaching the magnet.
FIG. 14 is an exploded perspective view showing a method in which magnet 8A of a thickness smaller than that of the magnet holder 6 is attached to the magnet holder 6.
On a workboard 30 on which the magnet holder 6 is to be mounted, a pair of jigs 31 each having a thickness half of the difference between the thickness of the magnet holder 6 and that of the magnet 8A are fixed so as to correspond to the magnet insertion windows 6A of the magnet holder 6.
The magnet holder 6 is mounted on said workboard 30 as shown by an arrow G so that the jigs 31 are received in the magnet insertion windows 6A When the magnet 8A is inserted into the magnet insertion window 6A as shown by an arrow H, the jig 31 is positioned under the magnet 8A, so that the magnet 8A is arranged at the center of the magnet holder 6 in the thickness direction thereof.
After that, as shown in FIG. 15, a bonding agent 32 is applied on the area of boundary between the magnets 8A and the windows 6A, and after the bonding agnet 32 has dried up, the holder 6 with magnets is reversed, and the bonding agent is applied on the perimeters of the magnets 8A and the windows on the opposite main surfaces thereof. With the operation mentioned above, the magnets 8A are fixed at the center of the magnet holder 6 in the thickness direction thereof, completing the vibrator of the electromagnetic diaphragm pump.
When the magnets 8A are thus placed at the center of the magnet holder 6 in the thickness direction thereof, the center of gravity of the vibrator is positioned on the line passing through the connection points of a pair of diaphragms 4 to the magnet holder 6, so that the balance of the reciprocation of the vibrator can be maintained in a good condition.
The above described prior art had the following problems.
When the magnets 8A with the thickness smaller than that of the magnet holder 6 are attached to the magnet holder 6, the jigs 31 are required, and since the bonding agent must be applied on both surfaces of the magnet holder 6 and the magnets 8A, the assembling of the vibrator is cumbersome.